1. Field of the Invention
The present invention generally relates to a printer apparatus, and more particularly to a portable thermal printer apparatus having a first module detachably attached to a second module.
2. Description of the Related Art
In recent years, there is a growing demand for portable thermal printers that can print, for example, barcodes and meter readouts. Compared to a general printer, a higher printing precision with respect to a paper conveying direction is required since barcodes and meter readouts are read by OCR (Optical Character Recognition).
With a conventional portable thermal printer of a clamshell type, when a cover of the printer is closed, a platen roller formed of rubber, holding a sheet of paper, presses against a thermal head. The platen roller is rotated by a motor, and the paper is fed by the frictional force of the platen roller. A conventional example is shown in Japanese Laid-Open Patent Application No.2002-120389.
Owing that the platen roller presses against the thermal head, the platen roller is generally formed of rubber. Although a satisfactory performance may be obtained in the early periods of using the rubber platen rollers, it is difficult to maintain such performance for a long period due to such factors as, for example, expansion/contraction caused from heat, deterioration with age, or wear.